21 Jan 2010:
Pollution from Asia
Boosts Ozone Levels in Western U.S.
Ozone and smog produced in China and southeast Asia is being blown across the Pacific Ocean on springtime winds and is increasing levels of ozone in the skies above the western U.S.
, according to a study published in the journal Nature
. The study, which examined 100,000 measurements taken by airplanes two to five miles above the ground, helps explain why background levels of ozone have increased by roughly 30 percent in the western U.S. since 1984, even as ground level ozone has dropped because cities and states have adopted stricter pollution control measures. Independent experts said the study showed the growing impact of cross-border pollution and noted that smog wafting from Asia could complicate efforts by the U.S. Environmental Protection Agency to reduce ozone pollution by up to 20 percent. Owen R. Cooper, a University of Colorado atmospheric chemist who led the study, said that ozone levels above the western U.S. doubled when prevailing winds blew from south and east Asia in the spring. Using computer programs that compared measurements taken in the U.S. with wind patterns from Asia, the scientists traced a significant percentage of the ozone pollution to Asian countries.
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